This invention relates to sockets for connecting integrated circuit packages to an electrical system; and more particularly, it relates to zero insertion force sockets.
An integrated circuit package consists essentially of an integrated circuit chip which has leads attached to bonding pads on the chip and which is encapsulated in a protective media. Typically, the system to which the integrated circuit package is to be connected is contained on one or more printed circuit boards.
In some systems, the integrated circuit package is soldered directly to the printed circuit board to thereby completely eliminate the use of a socket. However, such a direct solder connection is undesirable in that it makes the task of replacing a defective integrated circuit package on the circuit board relatively difficult.
By comparison, when the integrated circuit package is connected to the board by means of a zero insertion force socket, the socket is soldered to the board, and the package is held in the socket by some mechanical mechanism. That mechanism has one operating position which holds the socket contacts securely against the package leads, and it has another operating position which releases the package from the socket.
However, a major problem with a zero insertion force socket is that each of the mechanical components of the socket must be allowed some dimensional tolerance in order to make the socket manufacturable. And those dimensional tolerances cause the force with which the package is held in the socket to vary.
Particular care must be taken to ensure that the force with which the integrated circuit package is held does not become so large that the contacts in the socket permanently deform. On the other hand, care must be taken to ensure that the force with which the package is held in the socket does not become so small that good electrical connection between the package leads and the socket contacts is not made.
Further, the above problems must be solved while maintaining a small spacing between the socket contacts. Otherwise the socket would be too large and would occupy too much space on the printed circuit board.
Accordingly, a primary object of the invention is to provide an improved zero insertion force socket for holding an integrated circuit package.
Still another object of the invention is to provide a zero insertion force socket which does not overstress or understress the socket contacts despite the presence of dimensional tolerances in the socket components.